How did the evolution of the dinosaur claw evolve into the
current bird form? A new University of Bristol study into the claws of a group
of theropod dinosaurs, known as therizinosaurs, has revealed a great
versatility in their usage. Theropod dinosaurs, a group that includes such famous species as
Tyrannosaurusrex and Velociraptor, are often regarded as
carnivorous and predatory animals, using their sharp teeth and claws to capture
and dispatch prey. However, the detailed look at forelimb claws demonstrates
that these claws were very likely to have been used for other tasks.

ADVERTISEMENT

Inspired by this broad spectrum of claw morphologies, Dr.
Stephen Lautenschlager from Bristol's School of Earth Sciences studied the
differences in claw shape and how these are related to different functions.

His research focused on the therizinosaurs, an unusual group of theropods,
which lived between 145 and 66 million years ago. Therizinosaurs were very
large animals, up to 7m tall, with claws more than 50cm long on their
forelimbs, elongated necks and a coat of primitive, down-like feathers along
their bodies. But in spite of their bizarre appearance, therizinosaurs
were peaceful herbivores.

Dr. Lautenschlager said: "Theropod dinosaurs were all
bipedal, which means their forelimbs were no longer involved in walking as in
other dinosaurs. This allowed them to develop a whole new suite of claw
shapes adapted to different functions."

In order to fully understand how these different claws on the
forelimbs were used, detailed computer models were created to simulate a
variety of possible functions for different species and claw morphologies.

The dinosaur claws were also compared to the claws of mammals,
still alive today, whose function (that is, how and for what the claws are
used) is already known.

In the course of evolution, several theropod groups, including
therizinosaurs, changed from being carnivores to become plant-eaters.
This new study reveals that, during this transition, theropod dinosaurs
developed a large variety of claw shapes adapted to specific functions, such as
digging, grasping or piercing.

Dr.
Lautenschlager said: "It's fascinating to see that, with the shift from a
carnivorous to a plant-based diet, we find a large variety of claw shapes
adapted to different functions. This suggests that dietary adaptations
were an important driver during the evolution of theropod dinosaurs and their
transition to modern birds."